Do not reload code inside gr.NO_RELOAD context

[freddyaboulton]

Description

Adds a gr.NO_RELOAD symbol. Any code in a if gr.NO_RELOAD code-block will not be re-evaluated when the source file is reloaded. Helpful for importing modules that do not like to be reloaded (tiktoken, numpy) as well as database connections and long running set up code.

Sample usage:

import gradio as gr
import os

if gr.NO_RELOAD:
    print("IMPORTING")
    import tiktoken
    import numpy as np

def image_mod(image):
    print(np.zeros(5))
    return image.rotate(45)


cheetah = os.path.join(os.path.dirname(__file__), "images/lion.jpg")

demo = gr.Interface(image_mod, gr.Image(type="pil", value=cheetah, label="Input"), "image",
    flagging_options=["blurry", "incorrect", "other"], title="Testing a title!", examples=[
        os.path.join(os.path.dirname(__file__), "images/lion.jpg"),
        os.path.join(os.path.dirname(__file__), "images/cheetah1.jpg")
        ])

if __name__ == "__main__":
    demo.launch()

Attached gif below, note that the "IMPORTING" statement is not printed during reloads (only when first running the file as expected).

Also tested:

• modifying a file imported in the main demo file. Works as expected.
• gradio cc dev. Works as expected
• Also adds a reload mode test

Closes: #5402
Closes: #7123
Closes #6214

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---

Install Gradio from this PR

pip install https://gradio-builds.s3.amazonaws.com/79f17950ca3192cebd3a5da3e416ca644ddcefd7/gradio-4.22.0-py3-none-any.whl

Install Gradio Python Client from this PR

pip install "gradio-client @ git+https://github.com/gradio-app/gradio@79f17950ca3192cebd3a5da3e416ca644ddcefd7#subdirectory=client/python"

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Do not reload code inside gr.NO_RELOAD context

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[akx]

This will lead to interesting performance characteristics if the the tempdir ends up on a different file system, I'm sure.

[freddyaboulton]

I realized we don't actually need to do the copying

[abidlabs]

Would be good add gr.NO_RELOAD here: https://www.gradio.app/guides/developing-faster-with-reload-mode

[freddyaboulton]

Open for review - can wait until the release goes out!

[abidlabs]

It looks like ast.unparse was added in Python 3.9: https://docs.python.org/3/library/ast.html#ast.unparse

If we absolutely need this method, we could use this third-party implementation: https://github.com/simonpercivall/astunparse

[abidlabs]

Btw we should confirm that the reload tests are using 3.8 (otherwise, should not have passed)

[freddyaboulton]

Only 7 months until 3.8 EOL 🤩

I think we can manually modify the source code string so will look into it

[abidlabs]

Thanks @freddyaboulton, ping me whenever I can take another pass at the pr

[freddyaboulton]

@abidlabs this should be good for review now

[abidlabs]

Very cool @freddyaboulton and easy to use!

As I was testing, I noticed two things:

1. Now, when I run a file using gradio app.py, the entire contents of the file get executed twice initially. To repro, create a file called app.py with these contents:

import gradio as gr
import numpy as np

print("2") 

if gr.NO_RELOAD:
    print("1")

demo = gr.Interface(
    lambda s: s, gr.Image(np.random.random((255, 255, 3))), gr.Image()
)

if __name__ == "__main__":
    demo.launch()

You'll see that this is printed to the terminal:
2
1
2
1

2. I had expected that if gr.NO_RELOAD: is present in a file that is imported from the main file, it would also work -- since not all heavy imports are necessarily included in the main file. However, that does not seem to be the case. For example, if you have a second file called run.py and you import it from app.py with:

import gradio as gr

if gr.NO_RELOAD:
    print("3")

You'll noticed that "3" will be printed to the terminal every time that the original file is changed.

[freddyaboulton]

Thanks for the review @abidlabs ! I've addressed all of the comments you left in the PR. For point 1, that's expected. In order to reload the modules in the thread running the reloader, the modules need to be first imported. Point 2 should be fixed now!

[abidlabs]

Good stuff @freddyaboulton! Love the fact that we now have a test for reload mode

[freddyaboulton]

Thanks for the review @abidlabs ! Excited to release this